Core Leader: Thorsten R. Mempel. The Intravital Microscopy Core (Core A) has been formulated based on a stated need of U19 investigators and is designed to draw on the considerable experience of its key personnel in multiphoton intravital microscopy (MP-IVM) techniques to provide expertise and specialized equipment and aid in the design and execution of in vivo imaging studies of exRNA- and EV-mediated communication of glioblastomata with their stromal environment and the surrounding, healthy brain tissue. The Specific Aims ofthe Intravital Microscopy Core are as follows: 1. To provide expertise in the design of specific experiments utilizing multi-photon microscopy-based analysis of EV biogenesis by glioblastomata, their properties in the extracellular space and uptake by nonmalignant brain cells, as well as of functional exRNA- and EV-mediated intercellular communication between tumor cells and tumor stroma. 2. To provide access to the required instrumentation and to aid in the execution of MP-IVM experiments using mouse models of glioblastoma developed by the project Pis with assistance of the core as outlined in aim 1. 3. To provide computational resources forthe storage, processing, in-depth analysis, and interpretation of digital imaging data generated in aim 2.